Involvement of branched-chain amino acid aminotransferases in the production of fusel alcohols during fermentation in yeast

Organoleptic compounds produced by yeast during the fermentation of wort ha ve a great impact on beer smell and taste. Among them, fusel alcohols are t he major abundant volatile compounds. The availability of Saccharomyces cer evisiae mutants in which the genes coding for the two branched-chain amino acid aminotransferases have been deleted offers the possibility of further defining the role of these enzymes in the formation of higher alcohols. Com paring the production profiles of different strains, it is clear that they are not all influenced in the same way by branched-chain amino acid aminotr ansferase mutations. First of all, as propanol is synthesised from alpha -k etobutyrate, the first metabolic intermediate in the anabolic pathway of is oleucine, neither the eca39 nor eca40 mutations have any effect on the prod uction of this higher alcohol. On the other hand, it can be concluded that the eca40 mutation has a drastic effect on the production of isobutanol. To a certain extent, the same conclusion can be made for the production of ac tive amyl alcohol and isoamyl alcohol, although the results suggest that an other route could lead to the formation of these two higher alcohols.